The primary long term goal of the proposed research is an improved understanding of how blood cells are affected by passage through extracorporeal systems. Attention will focus initially on the erythrocyte and platelet. Within this context new knowledge is sought concerning the structure of the red cell membrane and its mechanical and transport properties. The approach will be essentially experimental. The studies planned will concentrate on the following objectives: (1) flow induced alterations, damage and destruction of human red cells and platelets; (2) effect of hemodialysis on sodium and potassium transport in the red cells of uremic patients; (3) mechanical properties of the red cell membrane and how these relate to molecular constituents and ultrastructure of the membrane; (4) oxygenation of blood in turbulent flow.